He could always have another miraculous "recovery" left in him. I'm pretty sure that a school that is rich in 4 and 5 star talent and willing to give him complete control over the program has some sort of catalyst that can trigger Urban Meyer's amazing health recovery.
I suspect that he could easily elevate USC back to the top, but this time, with all of the suspicious eyes still trained on USC (ever since Pete Carroll left), he would probably only be able to squeeze in 2-3 years before getting busted again.